1. Technical Field
The invention relates generally to the field of composite structures, and more particularly to the framing members with integrated flow channels for use in certain manufacturing processes.
2. Description of the Related Art
A variety of manufacturing techniques are known for assembling composite structures. For example, the spray lay-up method has been used for many years with good success. In spray lay-up systems, chopped fiber together with a catalyzed resin is sprayed directly into an open mold. Structural reinforcing members such as stringers can be positioned in the mold prior to the application of the chopped fiber and resin for improving the overall strength and rigidity of the structure. For example, U.S. Pat. Nos. 5,429,066, 5,800,749 and 5,664,518 to Lewit et al. describe various types of reinforcing members that can be used for this purpose. The fiber, resin and stringers applied in this way are then left to cure.
Recently, environmental concerns have encouraged the development of new closed mold manufacturing processes intended to limit the release of potentially harmful chemicals. These include resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM), and other similar processes in which fabrics are laid up in a mold as a dry stack of materials and then sealed in a mold or vacuum bagged. Resin is then allowed to flow into the dry stack of materials forming a laminate. Disposable tubing can be used exterior to the mold or vacuum bag for facilitating the injection of resin at desired locations.
One issue with closed mold manufacturing techniques involves the problem of ensuring adequate resin distribution over the whole laminate sufficiently quickly before the resin has cured substantially. In some closed mold systems, resin flow is aided by the use of a knitted type of non-structural fabric which is included in laminate specifically for this purpose. However, the additional labor and cost of materials with these approaches are such that the simple addition of non-structural fabric to the laminate has not entirely solved the problem of ensuring fast and complete distribution of resin. Accordingly, it would be desirable to provide a method and system for integrating a resin flow mechanism in composite structure manufacturing processes that minimizes the need for non-reusable external processing components (such as disposable tubing), and provides consistent results with only a minimal amount of additional time, labor and cost.